How to fix a nail-breaking slipjoint spring?

[hsherzfeld]

I have a Tree Brand Barlow with an absolute nail-breaking pen blade spring, and the clip blade spring could stand to be less stiff as well. I actually cut myself yesterday when I was using a screwdriver to open the pen blade and it slipped. Are there any minimally invasive methods to reduce spring stiffness? All I can think of is sanding down the back of the knife to reduce the spring cross-section (and therefore the bending moment).

 

[Bill DeShivs]

Without removing the rear and middle pins, that's all you can do.

 

[Another Shepherd]

I have a SAK that I cannot open barehanded. I have been known to use my ancient SOG multitool to open the SAK. But I have been tempted by the A.G. Russell Steel Thumbnail, $7.95 plus shipping.

 

[RoyalHolic]

Best thing I can suggest is to look into a thumb bar or thumb stud and try that? Won't alleviate tension but it will make it easier to at least open safely.

 

[pease]

Have you tried washing it in hot water then oiling it after it dries?

 

[davek14]

I love those Boker Barlows
What I've done for knives I've loved less (but, still good, old, knives) is to clamp the blade in a vise (soft jaws, of course), put on leather gloves, and open and close it a bunch of times. This may fatigue the spring, and I'm sure someone will weigh in on that, but it will definitely wear the blade where it rides on the spring. Don't oil it first and flush and oil it after.
One time, I did this and actually wore the part that contacts the spring too much and scored it. So, personally, I wouldn't risk it on a Boker Barlow.

 

[TheOne45]

Have you tried washing it in hot water then oiling it after it dries?

to clamp the blade in a vise (soft jaws, of course), put on leather gloves, and open and close it a bunch of times.

Is this knife old? Was so hard to open from the first day?
Could be some gunk or junk in the pivot area which makes the knife hard to open. Is it possible the pivot pin is hammered to much and this makes the knife hard to open?

I would follow those two quoted suggestions.
I would clamp the blade in a vise, spray some WD40 or other penetrating cleaner around the pivot and open/close the knife a few times. Hopefully this would remove some junk if there is.
Then I would oil the pivot area and try the knife how it opens. If still hard, I would use WD40 again to flush the oil from pivot area.
Then I would clamp the blade in a vise again and do some open/close procedure (like in second quote) to make the knife more ''open friendly''. You will feel when the knife starts to open more smoothly - you will need less force to do open/close action. Don't rush. Do it in steps so you won't over do it.

I have a Tree Brand Barlow with an absolute nail-breaking pen blade spring, and the clip blade spring could stand to be less stiff as well. I actually cut myself yesterday when I was using a screwdriver to open the pen blade and it slipped.

If you need a screw driver to open a knife I would make a joke and say.... carry a pliers in your other pocket for the next time when you need to open the knife. At least you won't cut yourself.
Seriously; if you need a screw driver to open it I would say such a knife is useless. I would do what I described.

If the knife has some sort of value (sentimental or in money) and you are afraid to make some sort of damage I would just put it in the showcase and buy a new knife.
There is also a third option, of course .... to buy a nice small pocket friendly pliers.

 

[hsherzfeld]

Have you tried washing it in hot water then oiling it after it dries?

No, I haven’t, mainly because the knife has bone scales and I’m not sure how immersion in hot water will affect them.

 

[hsherzfeld]

I love those Boker Barlows
What I've done for knives I've loved less (but, still good, old, knives) is to clamp the blade in a vise (soft jaws, of course), put on leather gloves, and open and close it a bunch of times. This may fatigue the spring, and I'm sure someone will weigh in on that, but it will definitely wear the blade where it rides on the spring. Don't oil it first and flush and oil it after.
One time, I did this and actually wore the part that contacts the spring too much and scored it. So, personally, I wouldn't risk it on a Boker Barlow.

I’ve considered that, but haven’t done it for the same reason: I don’t want to wear out the heel of the blade. I’ve also considered opening the blade to the spring’s maximum deflection and leaving it in that position for a while in the hope of weakening the spring, but I’ve also heard that such treatment can cause the spring to snap.

 

[pease]

I use a little dish soap, a drop or two at the pivot open the blade and wiggle it back-and-forth a little bit, then run it under hot water from the sink wiggling it back-and-forth. I never really soak my knives in water in a few minutes. Just dried off the best you can and let it sit dry or go straight to WD-40 at that point. A lot of times on some knives there’s some polishing compound that is dried from when they manufactured or cleaned up the knife around the pivot.

 

[Bill DeShivs]

I doubt that dirt is causing the knife to be hard to open.
Opening the blade to maximum spring deflection won't hurt the spring- but it won't help the opening, either.
File the head off the backspring pin, drive it out, and pull the springs up. Put each one in a vise and carefully file the spring to remove material. Use a dummy pin to test the pull until it's where you want it.

 

[hsherzfeld]

I doubt that dirt is causing the knife to be hard to open.
Opening the blade to maximum spring deflection won't hurt the spring- but it won't help the opening, either.
File the head off the backspring pin, drive it out, and pull the springs up. Put each one in a vise and carefully file the spring to remove material. Use a dummy pin to test the pull until it's where you want it.

Just to be clear, are you saying to remove material from the back (outside) surface of the springs or the front (inside, where the blade heel makes contact)?

 

[Guy McVer]

I have a Tree Brand Barlow with an absolute nail-breaking pen blade spring, and the clip blade spring could stand to be less stiff as well. I actually cut myself yesterday when I was using a screwdriver to open the pen blade and it slipped. Are there any minimally invasive methods to reduce spring stiffness? All I can think of is sanding down the back of the knife to reduce the spring cross-section (and therefore the bending moment).

Just oil it and keep working it open and shut. It may take a while, but it should eventually loosen up.

I had to do this with all three blades on an old stockman. When I started, I was breaking fingernails trying to open the blades, and I think I even used pliers a couple of times.

It took a lot of time, so what I did was just grab it and start working it open and shut whenever I had a few moments, and then put it back down again to come back to it later. Eventually all three blades got to the point that they open easily.

 

[Bill DeShivs]

Both- you CAN grind down the outside of the backsprings.
The really correct way to do it is to remove the metal from the inside of the springs- but not where the backspring contacts the blade tang/ Between there and the center pin on the inside.

 

[Guy McVer]

If you are dead set on removing material, then I wouldn't mess with the springs. I'd leave them alone and just file the area around the tang of the blade that contacts the spring.

In my opinion it's better not to mess with the springs. When you remove material from the spring, you are messing with the tension throughout every position that the knife is in as you deploy it. This should also affect how firmly the spring holds open the knife. That's probably something you don't want to weaken.

If on the other hand you file the tang, you can specifically target key areas of it so that you can control the amount of tension at specific positions of the blade as it is unfolding. For example you can weaken the spring tension just at the point that the knife is fully closed, so that initially getting it open is easier, but the amount of tension throughout the rest of the unfolding process remains the same. Hope that makes sense.

Point is that you can do more specific fine tuning by filing the tang of the knife where it contacts the spring instead of filing the spring. Filing the spring doesn't allow you to have that same level of control over the end result. All you're doing by filing the spring is weakening it, which I think is something to be avoided.

 

[killgar]

The geometry of the blade tang is important for holding the blade closed. Altering the geometry of the tang could easily result in a blade that won't stay closed.

The two bottom knives in the pic below had overly stiff back springs, so I did exactly as Bill DeShivs recommended, removed steel from the inside of the spring little by little, repeatedly assembling the knife to test, until I got them just right. I was very happy with the result. This was a mod I performed about ten years ago, the knives have been opened and closed several hundreds of times since, and I've never noticed any issues with weak springs.

Bill DeShivs is an actual real-life expert on old-school knife repair, including making knife springs from scratch. I'd take his word on how to deal with an overly stiff spring.

 

[TheOne45]

Bill DeShivs is an actual real-life expert on old-school knife repair, including making knife springs from scratch. I'd take his word on how to deal with an overly stiff spring.

For someone, who has some tools, a basic technical knowledge and at least half skillful hands this would be a wonderfull challenge for a rainy day.
There are also some nice videos on Youtube explaining and showing how slipjoint folders work.

 

[Guy McVer]

The geometry of the blade tang is important for holding the blade closed. Altering the geometry of the tang could easily result in a blade that won't stay closed.

The two bottom knives in the pic below had overly stiff back springs, so I did exactly as Bill DeShivs recommended, removed steel from the inside of the spring little by little, repeatedly assembling the knife to test, until I got them just right. I was very happy with the result. This was a mod I performed about ten years ago, the knives have been opened and closed several hundreds of times since, and I've never noticed any issues with weak springs.

Bill DeShivs is an actual real-life expert on old-school knife repair, including making knife springs from scratch. I'd take his word on how to deal with an overly stiff spring.

Having done modifications to both springs and tangs, I respectfully disagree.

Just think about this logically for a minute. Picture it in your head if you can. Think about the part of the blade tang that contacts the spring when the blade is closed. That part of the tang is no longer in contact with the spring when the blade is open. It's sitting on the opposite side of the pivot where the spring can't even touch it. This means that modifying this part will not affect how the spring holds the blade open.

What I described in my earlier post is perfectly reasonable and I know from my own experience that it works. Specifically, I know that overcoming the initial force of opening the blade can be accomplished by only filing one small area of the blade tang, while leaving the rest untouched, thus not affecting the fully deployed position of the knife. To me this is the most logical and practical approach requiring the least amount of modification. The amount of material needed to be removed should be extremely minimal as well. It doesn't take much.

On the other hand, any time you modify the spring, you structurally weaken it, which can lead to problems. It's more risky. And while it may turn out fine, the fact remains that it's not a necessary risk to take, at least not in this particular situation.

 

[killgar]

Having done modifications to both springs and tangs, I respectfully disagree.

What I described in my earlier post is perfectly reasonable and I know from my own experience that it works. Specifically, I know that overcoming the initial force of opening the blade can be accomplished by only filing one small area of the blade tang, while leaving the rest untouched, thus not affecting the fully deployed position of the knife. To me this is the most logical and practical approach requiring the least amount of modification.

On the other hand, any time you modify the spring, you structurally weaken it, which can lead to problems. It's more risky. And while it may turn out fine, the fact remains that it's not a necessary risk to take, at least not in this particular situation.

I don't argue with the experience of others, nor do I argue to prove the success of my experience. If you say that your method worked for you, more power to you. More than one way to skin a cat.

If I read hsherzfelds issue right, he's having difficulty overcoming the spring when initially lifting the blade from the closed/fully seated position.

As far as removing steel from the tang, the only way to make it easier to lift the blade from the closed/fully seated position is to remove steel from the part of the tang that holds the blade in the closed/fully seated position. And removing any steel from the tang that holds the blade in the closed/fully-seated position increases the risk of negatively affecting how the blade sits when closed. Like possibly creating blade-peek, or the reverse- causing the blade to sit too deep and preventing one from getting their nail in the nail nick.

I didn't say anything about affecting the blade in the "fully deployed position".

If hshezfelds problem was, say, overcoming the halfway point during opening, then removing steel from the butt-end/bottom of the tang would, in my opinion, be an appropriate solution, and one that would not affect the blade in either the closed or fully-open position. But that doesn't sound like his problem.

Of course any modification to a knife, particularly removing steel from either the tang of the blade, or the spring, comes with risk. Whatever method hsherzfeld uses, I hope he can resolve the issue. One word of advice I would give him if he chooses to remove steel from the spring is to make sure he doesn't remove any from where the kick of the blade contacts the spring, otherwise that would affect how the blade sits when closed.

As far as our difference of opinion, I will respectfully agree to disagree .

 

[Guy McVer]

Well I don't want to argue in circles when I don't actually think the knife needs to be modified at all anyway. That implies a problem with its design or manufacturing. I think the knife design and manufacturing are probably just fine, and all that needs to be done is just oil it generously and keep working the blades until they start opening more easily.

I've seen this same exact issue with a lot of older knives and resolved it myself with the same method. It just needs to be worked a bit. This is just something that happens with an old knife that hasn't been used for a long time.